3 Human impact on the environmentBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentHow does human activity affect the environment?

4 Boardworks GCSE Science: Biology Human Impact on the EnvironmentPopulation growthBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentThere are about 6.6 billion people in the world and over 95 million babies are born per year – that is an average of three babies per second!Has the rate of population growth always been the same?

5 Boardworks GCSE Science: Biology Human Impact on the EnvironmentExponential growthBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentThe human population is said to be growing exponentially. This means that the larger the population, the faster it grows.An increase in average life expectancy is largely responsible for the rapid increase in population. Why do people live longer than they did hundreds of years ago?better healthcare (hospitals, medicines, vaccines)more and better foodcleaner waterTeacher notesIt is important to note the use of the terms ‘economically developing nations’ and ‘economically developed nations’ to emphasise that this slide is referring to how economic factors, not cultural matters, can distinguish the relative development of nations.better sanitationThe biggest increase in population is in economically developing nations, rather than economically developed nations. Why do you think this is the case?

6 The changing populationBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesData from the Population Reference Bureau (www.prb.org). The second stage of this animated graph shows how the total population is distributed among more economically developed countries and less economically developed countries. Students should be made aware that the two sections of the graph add up to 100% of the population and are not overlaid. So, in the year 2000, for example, more economically developed countries made up approximately 20% of the total population, with the remaining 80% being located in less economically developed countries.Students could be asked to come up with reasons for the difference in population changes between more and less economically developed countries in the 20th century and beyond.

7 Predicting future growth rateBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentComputer models can be used to make predictions about population growth by using assumptions about birth rate.Most analysts assume that birth rates will fall within the next 50 years. Why do you think this might happen?decreased fertilitylack of resourcesdiseasewarHow important do you think predictions about climate change and unsustainable development are in the analysts’ calculations?

9 Boardworks GCSE Science: Biology Human Impact on the EnvironmentWhat are pollutants?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentOne of the biggest problems of a rising population is an increase in pollution.A pollutant is a substance that contaminates air, water or land. Some pollution is caused by natural events such as volcanic eruptions, but the majority is caused by human actions. Pollutants are either:non-degradable (e.g. the pesticide DDT) – these decompose extremely slowly, allowing them to accumulate to toxic levels as they are passed along food chains.biodegradable (e.g. sewage) – these are usually only damaging when added to the environment more quickly than they can decompose.

12 Boardworks GCSE Science: Biology Human Impact on the EnvironmentAir pollutionBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentHuman activity produces two main types of air pollutant:noxious gases – These include carbon dioxide (CO2), sulfur dioxide (SO2) and nitrogen oxides (NOx).particulates – These are tiny particles suspended in air (e.g. smoke), which are usually produced by the combustion of fossil fuels.Air pollution has been a major problem since the Industrial Revolution of the late 18th Century, and has been made worse by humans’ reliance on burning fossil fuels for energy.Teacher notesSee the ‘Earth’s Atmosphere’ chemistry presentation for more information on the atmosphere and air pollution.Air pollution, global warming, acid rain, damage to the ozone layer and smog. Each of these has serious implications for the environment and human health.

13 Global warming and greenhouse gasesBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentOne of the greatest threats caused by air pollution is global warming. Global warming is caused by a build-up of greenhouses gases, which leads to an increase in the Earth’s temperature.A greenhouse gas is an atmospheric gas that absorbs infrared light.Key greenhouses gases include:carbon dioxide (CO2)Teacher notesSee the ‘Climate Change’ chemistry presentation for more information on greenhouse gases, the greenhouse effect and global warming.methane (CH4)water vapour (H2O)nitrous oxide (N2O)

14 Boardworks GCSE Science: Biology Human Impact on the EnvironmentThe greenhouse effectBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis four-stage animation can be used to illustrate the principles of the greenhouse effect. Students could be asked to consider the impact of rising greenhouse gases on the natural phenomenon of the greenhouse effect.

15 Atmospheric carbon dioxideBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis graph was produced using data sourced from the Mauna Loa Observatory, Hawaii, courtesy of NOAA (the National Oceanic and Atmospheric Administration). More information about atmospheric gases is available at

16 Boardworks GCSE Science: Biology Human Impact on the EnvironmentCarbon dioxide levelsBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentCarbon dioxide is one of the most important greenhouse gases because atmospheric concentrations have risen dramatically over the past century. Why do you think this is?Burning fossil fuels, deforestation and flooding land for the construction of hydroelectric dams have all contributed to rising levels of carbon dioxide.How many examples of burning fossil fuels can you think of? Are there any alternatives?

17 Boardworks GCSE Science: Biology Human Impact on the EnvironmentWhat is the carbon sink?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentBefore the industrial revolution, carbon dioxide levels were usually kept in check by the carbon sink – forests and oceans that capture and store carbon.forests – All green plants absorb carbon dioxide as part of photosynthesis. The absorbed carbon is only released back into the atmosphere when the plant dies and rots, or is burned.oceans – Carbon dioxide dissolves in sea water, depending on the temperature and pressure. Tiny marine animals called phytoplankton extract carbon from the carbon dioxide to make their skeletons and shells.

19 Boardworks GCSE Science: Biology Human Impact on the EnvironmentAcid rainBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis six-stage animation can be used to illustrated the principles of acid rain. The final stage of the animation shows that the effects of acid rain are not limited to the country causing the pollution. This could be used to stimulate a small group or whole class discussion.

20 What damages the ozone layer?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentThe ozone layer is a protective part of the atmosphere that absorbs some of the Sun’s damaging ultraviolet (UV) rays.Damage to the ozone layer means that more UV rays reach Earth, increasing the risk of skin cancer.The ozone layer is damaged by chemicals called chlorofluorocarbons (CFCs), which contain the elements carbon, hydrogen, chlorine and fluorine.CFCs are used in fridges and freezers, aerosol sprays and packaging materials such as polystyrene. The production and use of CFCs is now banned in many countries and could be worldwide in a few years.

24 Boardworks GCSE Science: Biology Human Impact on the EnvironmentEutrophicationBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis five-stage animation illustrates the process of eutrophication. Suitable prompts could include:Why do fertilisers make algae grow?Increased amount of algae will reduce the amount of sunlight reaching plants. What effect will this have?What will happen to the dead plants?Why will bacterial decomposition of plants affect fish and other animal life in the lake?

25 Boardworks GCSE Science: Biology Human Impact on the EnvironmentEutrophicationBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis ordering activity could be used as a plenary or revision exercise on eutrophication. Mini-whiteboards could be used to make this a whole-class exercise.

27 Boardworks GCSE Science: Biology Human Impact on the EnvironmentLand pollutionBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentLand and soil can be polluted by two main types of substance:solid waste – such as plastic, metal, paper and other man-made substanceschemicals – such as herbicides and pesticides, crude oil and waste from industrial processes.Photo credit: Marcel HolLand pollution often leads to water pollution, as chemicals are washed into rivers and lakes.

28 Boardworks GCSE Science: Biology Human Impact on the EnvironmentHow much waste?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentEvery year, billions of tonnes of paper, plastics, synthetic materials, metal and wood are thrown away.On average, each UK household produces over 1 tonne of rubbish each year.How could you estimate the amount of rubbish you throw away each year?Photo credit: Paco Navarro (www.ohestudio.com)

29 Boardworks GCSE Science: Biology Human Impact on the EnvironmentWhat are the options?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentWhat methods are there for disposing of waste materials?Landfill is the cheapest solution, but sites quickly become full and the waste contaminates the surrounding air, soil and water.Incinerating waste reduces volume, but often produces toxic chemicals.Recycling materials allows them to be useful again, and reduces the need to use more raw materials.Teacher notesSee the ‘Making Polymers’ chemistry presentation for more information on disposing of plastics.Composting uses natural biological processes to decompose organic materials, but cannot be used to dispose of non-biodegradable waste.

30 What is the best solution?Boardworks GCSE Science: BiologyHuman Impact on the EnvironmentThe best way to deal with waste is to produce less of it!It takes 100 kg of resources to make 10 kg of shopping, and most of that ends up in the bin.If products were redesigned to be biodegradable or easier to recycle, the amount of waste and disposal costs would be significantly reduced.Photo credit: Vicky STeacher notesMore information on recycling is available atHow could you reduce the amount of waste you produce?

33 Boardworks GCSE Science: Biology Human Impact on the EnvironmentGlossary (1/2)Boardworks GCSE Science: BiologyHuman Impact on the Environmentbiodiversity – The number of different species within a specific habitat.chlorofluorocarbon – A chemical that damages the ozone layer.eutrophication – Over-enrichment of water with nutrients, causing excessive algal growth and reduced oxygen levels.global warming – The rise in the Earth’s temperature caused by an increase in greenhouse gases from human activity.greenhouse gas – A gas that traps the Sun’s infrared radiation in the Earth’s atmosphere.

34 Boardworks GCSE Science: Biology Human Impact on the EnvironmentGlossary (2/2)Boardworks GCSE Science: BiologyHuman Impact on the Environmentindicator species – An organism whose presence or absence provides information on environmental conditions.ozone – A gas that is toxic at ground level but which forms a protective layer higher in the Earth’s atmosphere.particulate – A type of pollution consisting of tiny particles, such as smoke.pollutant – A substance that contaminates air, water or land.smog – A hazardous type of air pollution containing ozone and particulates.

36 Boardworks GCSE Science: Biology Human Impact on the EnvironmentMultiple-choice quizBoardworks GCSE Science: BiologyHuman Impact on the EnvironmentTeacher notesThis multiple-choice quiz could be used as a plenary activity to assess students’ understanding of human impact on the environment. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.